In general, the present invention relates to automatic tool changers for machine tool spindles. More particularly, the invention relates to an automatic tool changer having a revolving holder to carry, index and drive a plurality of tools.
Automatic tool changers have been developed in response to the need of the machine-tool industry to perform multiple operations in a single set up, to re-tool quickly in order to accommodate product designs that are changing in timely response to market demands, and to be able to replace quickly a worn out or broken part. The typical solution to this problem utilizes a large library of tools stored in a tool storage magazine and accessible through various mechanisms, such as rotating arms, robots, rails and the like.
FIG. 1, for instance, shows the automatic tool changer described in U.S. Pat. No. 5,300,006 (JP 7060586), which incorporates a tool storage magazine mounted on a frame, the frame capable of sliding in and out of storage and rotating to replace a tool in a tool-engaging fixture, which is connected to the machine-tool spindle. The tool-changing operation is computer-controlled by means of an input terminal mounted on the machine frame. This type of solution to the frequent re-tooling problem produces large and complex tool changing equipment, which is expensive and cumbersome, at least for more modest operations or for operations requiring more flexibility and agility in response to changing market demands.
Another solution has been to house in the machine-tool spindle head an integrated tool cartridge or tool turret of about six different tools so that the proper tool is indexed into position as and when needed. A machine-tool revolving head, which is typical of the prior art and described in U.S. Pat. No. 5,146,663, is shown in FIG. 2. The prior-art revolving head incorporates a fixed frame, which is fitted with a turret having multiple tool-bearing spindles. The arrangement includes a driving shaft, which is connected at one end to a driving gear, and at the other end through a set of gears to the tool-bearing head of the spindle. The turret moves axially and rotates with respect to the frame by means of a hydraulic driving mechanism, which includes an axial piston, a rotary piston and a chamber.
One problem with integrating the turret or tool cartridge with the spindle head is that each time a new set of tools is needed, either the entire spindle head and tool turret assembly must be replaced, necessitating elaborate realignment procedures, or each tool must be replaced individually in a time-consuming and elaborate manner. To avoid realignment, save time and increase productivity while reconfiguring a machining system, it is desirable to be able to swap quickly a tool cartridge from one machine to another without elaborate procedures.
The subject invention provides a reconfigurable automatic tool changer (RATC), which allows a tool cartridge to be easily attached to or detached from any standard machine-tool spindle head. In the preferred embodiment, the reconfigurable automatic tool changer (RATC) is based on a modular design, comprising a revolving-head unit, or tool cartridge, having a plurality of tool holders, a meshing gear for engaging a tool holder with the spindle of the machine tool, and an adapter block for positioning the revolving-head unit on any standard machine-tool spindle head. The adapter block allows the RATC to be easily coupled to a wide variety of commercial machine-tool spindles, giving the subject invention a degree of portability not found in the prior art. The revolving head unit or tool cartridge also incorporates an inventive mechanism which allows tool indexing to be achieved by means of one actuator only, in contrast to prior art-designs.
This invention represents a substantial departure from prior art practice. In contrast to prior-art designs, the RATC is modular and portable, allowing the same revolving head-unit or tool cartridge to be used for various machine tool spindles. Compatibility is achieved by custom-designing the adapter block, rather than the revolving head, a task which is easier, more efficient and less costly. The tool holders on the revolving head are driven by the machine spindle head through a standard, off-the-shelf spur gear, which meshes with a corresponding gear on the tool holder. A single motor on the adapter block drives the revolving head unit and accomplishes the indexing function of the revolving head through a three-dimensional cam structure. This cam structure includes a set of bevel gears and indexing arms spaced at a distance equal to the radius of the cam circle, in order to accommodate three to six tools in a set.
The inventive design of the revolving-head unit or cartridge and the modularity of the entire adaptable automatic tool changer device create a simpler, more efficient and portable structure which is easier to reconfigure and does not require duplication of existing equipment in a manufacturing setting.